Examples of electronically controlled cartridge control valves for fuel injectors are shown in U.S. Pat. No. 5,494,219 to Maley et al., U.S. Pat. No. 5,407,131 to Maley et al., U.S. Pat. No. 4,869,462 to Logie et al., and U.S. Pat. No. 4,717,118 to Potter. In each of these examples, the injector includes a mechanically actuated fuel pumping plunger and an electronically actuated fuel pressure control valve assembly. The pressure control valve assembly includes a solenoid operated poppet valve that controls fuel pressure in the injector in order to control fuel injection delivery. Fuel pressure is controllably enabled to be developed within the injector by electrical actuation of the pressure control valve assembly. Fuel pressure is controllably prevented from developing within the injector by not electrically actuating the pressure control valve so that fuel can spill through a return passage while the plunger is undergoing a portion of its pumping stroke.
In such electronically controlled fuel injectors, the armature of the pressure control valve assembly moves the poppet valve in one direction until it engages a valve seat, and holds the poppet valve in its closed position to enable fuel pressure to be developed in the injector, eventually resulting in fuel injection. At the end of the fuel injection cycle, the solenoid is de-energized, and a return spring moves the poppet valve member off the valve seat, returning the poppet valve member to its open position, which prevents the development of fuel pressure by spilling the fuel back to a fuel reservoir.
In most of these type of valve assemblies, the valve body holding the solenoid is sealed against leakage of fuel out of the control valve. While fuel leakage out of the control valve can be accomplished in a number of ways known in the art, such as by using closed housings or appropriately positioned o-rings and the like, accommodating internal leakage within the cartridge control valve has proven somewhat more problematic. For instance, the slow build up of fuel pressure in the cavity containing the solenoid due to leakage between the poppet valve member and its guide bore can sometimes result in undesirable bouncing behavior on the part of the poppet valve member. Because this bouncing phenomenon can sometimes result in undesirable secondary injections, some means must be provided for relieving fuel pressure from the cavity containing the solenoid.
It has been observed that if a pressure relief passage from the cavity containing the solenoid is too small, undesirable secondary injections can still occur since adequate pressure relief cannot occur through a restricted pressure relief passage when the poppet valve member is moving from its closed to its open position. On the other hand, it has been observed that if the pressure relief passage is too large, pressure spikes can travel up through the pressure relief passage, into the cavity containing the solenoid and act upon one end of the poppet valve member causing the poppet valve member to briefly close, which again can cause undesirable secondary injections. It is well known in that art that abruptly ending each injection event and avoiding secondary injections can significantly improve hydrocarbon and particulate emissions.
The present invention is directed to overcoming one or more of the problems as set forth above.